Method for producing a cover for an integrated optical circuit and cover for an integrated optical circuit

ABSTRACT

A method for producing a cover for an integrated optical circuit, and an integrated optical circuit produced with this cover. The method minimizes the effort for the integration of optical components into fiber-optic systems by automatically positioning an optical component placed onto a mold punch. A liquid that can harden is poured around the optical component and the mold punch, and after this solidifies, it forms the cover.

STATE OF THE ART

The invention proceeds from a method for the production of a cover foran integrated optical circuit pursuant to the preamble of the mainclaim.

From patent application DE-P 42 12 208.2, a method for the production ofoptical polymer components with an integrated fiber chip coupling usingcasting technology is already known. Here, a polymer substrate is formedby means of a master structure, in order to couple an integrated opticalcircuit between two glass fibers, in such a way that the glass fiberscome to rest in the substrate in a V-shaped groove. In this connection,their longitudinal axis is flush with the longitudinal axis of alightwave guide channel arranged between the V-shaped grooves. Byfilling the grooves and the lightwave guide channel with polymeradhesive, when a polymer cover is placed on top, a mechanically strongbond between the substrate and the cover, as well as optical coupling ofthe glass fibers to the lightwave guide formed of polymer adhesive, isguaranteed.

Furthermore, from the article "Channel glass wave guide detectors withgrafted GaAs film in embedded configuration" in Electronic Letters 27(1991), pages 410 to 412 by Chan, Yi-Yan, et al., it is known to couplea photodetector grafted onto a glass substrate to a lightwave guidelocated in the substrate, in evanescent manner. This production methodrequires precise positioning of the wave guide and of the photodetectorrelative to one another, which must be carried out individually for eachcomponent, and comprises a complicated positioning method.

ADVANTAGES OF THE INVENTION

The method according to the invention, with the characterizing featuresof the main claim, has the advantage, in contrast, that a cover for anintegrated optical circuit is produced without positioning effort.Furthermore, there is the advantage that the method according to theinvention is particularly suited for mass production, since the locationof the optical component with regard to the mold punch is predeterminedor results without further intervention. Furthermore, an advantage ofthe method consists of positioning an optical module with regard tofiber guide grooves for holding lightwave guides, although the opticalcomponent is smaller in dimensions than the distance between the guideprojections provided for later holding light guides.

With the measures listed in the dependent claims, advantageous furtherdevelopments and improvements of the method indicated in the main claimare possible.

The accuracy of positioning of the optical component in the mold punchis increased in that at least one positioning device is arranged on themold punch, which positions the optical component on at least one side.

An advantageous arrangement consists of arranging two positioningdevices on the mold punch, which delimit the optical component onopposite sides.

The positioning process when placing the optical component onto the moldpunch is simplified in that the sides of the positioning device whichface the optical component are beveled and the corresponding sidesurfaces of the optical component are at least partially beveled. Inthis way, the tolerance of the component dimensions which arepermissible for automatic positioning of the optical component on themold punch are increased and the positioning process is simplified.

The method is improved by using mold punches which have stress reliefprojections. The pressure applied to the optical component when theoptical component is placed down is uniformly absorbed by the stressrelief projections. This achieves the result that optical componentsmade of brittle materials, particularly indium phosphide or galliumarsenide, are not damaged when they are placed on the mold punch. Theproduction method is particularly suitable for bonding photodetectors tointegrated optical lightwave guides, since here, particularly precisepositioning is necessary, which be achieved in simple manner with themethod according to the invention.

The cover according to the invention can be produced particularly easilyaccording to one of the methods named, and is particularly suitable foruse in an integrated optical circuit, where the lightwave guide isformed, in advantageous manner, by the adhesive which fills a groove inthe substrate, when the cover is bonded to a substrate. The integratedoptical circuit according to Claim 1 offers the advantage that thebonding of substrate and cover and the coupling of wave guides takesplace in one step. Production can be carried out in cost-effectivemanner.

DRAWING

Embodiments of the invention are shown in the drawing and explained ingreater detail in the following description. The drawing shows:

FIG. 1 the optical component,

FIG. 2 a mold punch 2, and

FIG. 3 a cover.

DESCRIPTION OF THE EMBODIMENTS

FIG. 1 shows the optical component 1, which in this select exampleconsists of a photodetector which was made from indium phosphide. Twogrooves 3 are made in the photodetector. The grooves 3 are arranged toalign with each other and run parallel to the detector zone 7. At thedetector zone 7, electrical incoming lines 14 are passed from theoutside edge of the optical component 1. In this example, the grooves 3are formed as V-shaped grooves. The grooves 3 are aligned with eachother and each lead part of the way into the optical component 1 fromthe outside edges of the optical component 1.

In a particularly simple embodiment, the optical component 1 has onlyone recess 3, which is preferably formed as a groove. The location andthe shape of the recess must be selected in accordance with the functionof the recess and the structure of the optical component.

FIG. 2 shows a mold punch 2, which has guide projections 4, projections12, positioning devices 6 and stress relief grooves 5. The guideprojections 4 lead part of the way into the surface of the mold punch 2from the outside edges of the mold punch 2. The guide projections 4 arepreferably arranged at a right angle to the outside edges of the moldpunch 2. The length of the guide projections 4 is determined by the factthat the guide grooves 11, which are preferably in V shape here, and aremolded by the guide projections 4, are used to hold lightwave guides.The guide projections 4 are furthermore arranged in alignment. In thisapplication example, the stress relief projections 5 run parallel to thealignment of the guide projections 4 and are arranged over the entiresurface of the mold punch 2, except for the region between the guideprojections 4. The stress relief projections 5 are preferably formed inV shape in this example. The size ratios of the stress reliefprojections 5 and the guide grooves 4 are not shown true to scale, sincethe height of the guide grooves 4 is on the order of 80 micrometers andthe height of the stress relief projections 5 is in the range around 5micrometers. The height and the width of the grooves 3 and theprojections 12 are structured in shape so that they are adapted to eachother and allow precise positioning of the optical component 1 withregard to the alignment of the guide projections 4, i.e. the opticalcomponent 1 is positioned precisely relative to the mold punch 2, bothlaterally and vertically.

Furthermore, two aligned projections 12 are arranged parallel to thealignment of the guide projections 4 between the region of the guideprojections 4. The mold punch 2 furthermore has two positioning devices6 which are arranged parallel to one another in a directionperpendicular to the alignment of the guide projections 4 and arelaterally offset. Between the positioning devices 6, additional stressrelief projections 5 are affixed parallel to the alignment of the guideprojections 4 in this example. The projections 12 are of the same orderof magnitude as the guide projections 4, i.e. approximately 80micrometers high. The projections 12 and the positioning devices 6 arestructured in V shape in this select example. The mold punch 2preferably consists of a metal which is galvanically cast from a siliconmold. In this example, nickel was selected as the metal.

In a simple version, the mold punch 2 has only one projection 12, inaddition to at least one guide projection 4. Correspondingly, theoptical component 1 also has only one groove 3. The location of theprojection 12 is adapted to the location of the groove 3. If severalprojections 12 are arranged, then their location can be selected tocorrespond to the location of the corresponding grooves 3.

In another, expanded embodiment, the mold punch 2 also has at least onepositioning device 6 in addition to at least one guide projection 4 andat least one projection 12.

The location and the shape of the positioning device 6 must be selectedin accordance with the function of the positioning device 6 and theshape of the optical component 1. The geometrical shape of the opticalcomponent 1 determines the shape of the positioning device 6.

FIG. 3 shows a cover 13 which was produced with the mold punch 2 shownin FIG. 2. The cover 13 has recesses 9. The recesses 9, which are offsetlaterally parallel to the alignment of the guide grooves 11 and arearranged between the guide grooves 11, were molded by the projections 12of the mold punch 2.

The recesses 9, which are arranged parallel to the alignment of theguide grooves 11 and parallel to one another over the border region ofthe optical component 1, were molded by the positioning devices 6 of themold punch 2. The location and orientation of the shaped opticalcomponent 1 has been outlined. The guide grooves 11, the recesses 9 andthe depressions 10 are stamped in polymer in this select example.

The production of the cover 13 for an integrated optical circuit isexplained using FIGS. 1 to 6.

A cover 13 for an integrated optical circuit with an optical component1, which is automatically positioned on guide grooves 11 for lightwaveguides in the production of the cover, is produced using a mold punch 2,as shown in FIG. 2. The optical component 1, as shown in FIG. 1, issmaller in dimensions than the distances between the guide projections 4of the mold punch 2. In order to allow lateral and vertical positioningof the optical component 1 in spite of this, positioning devices 6 andprojections 12 have been formed on the mold punch 2. The projections 12are aligned and are arranged laterally offset to the alignment of theguide projections 4. The optical component 1 shown in FIG. 1 has grooves3 which are arranged in alignment. The positioning devices 6 havebeveled side surfaces at the sides which face the optical component 1when the optical component 1 is laid down. In this select example, thepositioning devices 6 are structured as V-shaped projections. Betweenthe positioning devices 6, three stress relief projections 5 arearranged on the mold punch 2, parallel to the alignment of the guideprojections 4. The mold punch 2 has additional stress relief projections5 arranged parallel to the alignment of the guide projections 4 in theregion of the mold punch 2 which is covered when the optical component 1is placed onto the mold punch 2. In the alignment between the guideprojections 4, no positioning devices 6 or stress relief projections 5are arranged. When the optical component 1 is placed onto the mold punch2, the projections 12 engage in the grooves 3. This determines thelateral position of the optical component 1 with reference to thealignment of the guide projections 4. At the same time, the verticalposition is determined by the height difference of the projections 12and the grooves 3. Furthermore, the optical component 1 is held alongthe lateral outside edges 8 of the optical component 1 by thepositioning devices 6, and thus rotation or tilting of the opticalcomponent 1 when it is placed down is prevented. Since the opticalcomponent 1 is placed down under pressure, and many of the materialsused for the production of optical components, such as indium phosphide,are very brittle, bending and damage of the optical component must beprevented. This achieved in that the optical component 1 rests on thestress relief projections 5 of the mold punch 2 with a large part of itsentire surface. The optical component 1 now lies on the projections 12and the stress relief projections 5 with the grooves 3. For betterinsertion of the optical component 1 between the positioning devices 6,the lateral outside edges of the optical component 1 are at leastpartially beveled. This allows the lateral outside edges 8 and thebeveled side surfaces of the positioning devices 6 to slide against eachother when they come into contact. This reduces the pressure requiredfor positioning and increases the tolerances for the optical component 1with regard to the distance of the positioning devices 6. With thismethod, the contact wires 14, which lead from the outside edge to theactive zone 7 of the optical component 1, as shown in FIG. 1, are notcompletely covered by a polymer. This has the result that the electricalincoming lines 14 can be contacted without having to remove the polymer,i.e. the polymer can be removed without problems at the edge, in orderto be able to produce the contact.

For the production of the cover 13, the component 1 is placed onto themold punch 2. In order to ensure that the polymer gets into all theregions between the component 1 and the mold punch 2, the component 1 iswetted with liquid polymer before it is placed on the mold punch 2.Subsequently, a liquid which can harden, in this example a liquidpolymer, is poured around the positioned optical component 1 and themold punch 2. After the curing time of the liquid polymer, the moldpunch 2 is removed and a cover 13, as shown in FIG. 3, is obtained. Thiscover 13 now has depressions 10, which were molded by the stress reliefprojections 5, recesses 9 which were formed by the projections 12 andthe positioning devices 6, and guide grooves 11, which were formed bythe guide projections 4. The active zone 7 of the optical component 1,as shown in FIG. 6, is positioned with reference to the alignment of theguide grooves 11. For the production of an integrated optical circuit, asubstrate that has at least two, preferably V-shaped grooves is used.The distance, the size and the orientation of the V-shaped groovescorrespond to that of the guide grooves 11 of the cover 13. Anadditional groove is arranged between the two V-shaped grooves. Theintegrated optical circuit is covered with a transparent adhesive, wherethe additional groove lying between the V-shaped grooves is filled andthus forms a lightwave guide. A light guide, particularly light fibers,is inserted in each of the two V-shaped grooves. The V-shaped grooves inwhich the light guides are inserted are also covered with thetransparent adhesive. The cover 13 is placed onto the integrated opticalcircuit in such a way that the light guides are also held by the guidegrooves 11. The cover 13 is pressed down so firmly that only a thinlayer of transparent adhesive remains between the integrated opticalcircuit and the cover 13. When this is done, the recesses 9 anddepressions 10 are also filled with the transparent adhesive. In thismanner, an integrated optical circuit is produced, in which an opticalcomponent 1 located in a cover 13 is automatically positioned on thelightwave guide filled with adhesive and lying between the V-shapedgrooves when the cover 13 is glued on, where the lightwave guide isformed by filling the additional groove with adhesive.

The production method described can also be applied analogously to moldpunches 2 which have only at least one guide projection 4 and at leastone projection 12 or at least one guide projection 4 and at least oneprojection 12 and one positioning device 6.

For simple positioning of the optical component 1, it is sufficient ifthe optical component 1 is positioned by at least one projection 12.

Precise positioning is achieved if the mold punch 2 has at least onepositioning device 6 in addition to the projection 12, which positionsthe optical component at an outside edge.

I claim:
 1. An assembly for an integrated optical circuit comprising:a)an optical component having at least one groove extending to an outsideedge of the optical component; b) a cover having at least one recessextending the groove of the optical component away from the outside edgeof the optical component and a guide groove to hold light guides; and c)an integrated optical circuit comprising a substrate that has at leasttwo first grooves and an additional groove located between the at leasttwo first grooves, wherein the cover of the optical component isattached to the substrate by an optically transparent adhesive, whereinthe optically transparent adhesive also fills the additional groovelying between the at least two first grooves, and wherein the cover andthe substrate are positioned laterally with respect to one another sothat the guide grooves of the cover are arranged above the at least twofirst grooves of the substrate to form guide channels in which the lightguides extending in the direction of the additional groove are received.2. The assembly according to claim 1, wherein the cover has at least oneadditional recess adjacent to the outside edge of the optical component,the additional recess corresponding to a shape of a positioning deviceof a punch mold.
 3. The assembly according to claim 1 wherein the coverhas depressions corresponding to stress relief projections of a punchmold.
 4. The assembly according to claim 1 wherein the optical componentis a photodetector.